Thermoelectric Properties of Two-Phase PbTe with Indium Inclusions

The thermoelectric figure of merit (zT) can be increased by introduction of additional interfaces in the bulk to reduce the thermal conductivity. In this work, PbTe with a dispersed indium (In) phase was synthesized by a matrix encapsulation technique for different In concentrations. x-Ray diffraction analysis showed single-phase PbTe with In secondary phase. Rietveld analysis did not show In substitution at either the Pb or Te site, and this was further confirmed by room-temperature Raman data. Low-magnification (similar to 1500x) scanning electron microscopy images showed micrometer-sized In dispersed throughout the PbTe matrix, while at high magnification (150,000x) an agglomeration of PbTe particles in the hot-pressed samples could be seen. The electrical resistivity (rho) and Seebeck coefficient (S) were measured from 300 K to 723 K. Negative Seebeck values showed all the samples to be n-type. A systematic increase in resistivity and higher Seebeck coefficient values with increasing In content indicated the role of PbTe-In interfaces in the scattering of electrons. This was further confirmed by the thermal conductivity (kappa), measured from 423 K to 723 K, where a greater reduction in the electronic as compared with the lattice contribution was found for In-added samples. It was found that, despite the high lattice mismatch at the PbTe-In interface, phonons were not scattered as effectively as electrons. The highest zT obtained was 0.78 at 723 K for the sample with the lowest In content.

Wallner lines, crack velocity and mechanisms of crack nucleation and growth in a brittle bulk metallic glass

Mode I fracture experiments were conducted on brittle bulk metallic glass (BMG) samples and the fracture surface features were analyzed in detail to understand the underlying physical processes. Wollner lines, which result from the interaction between the propagating crack front and shear waves emanating from a secondary source, were observed on the fracture surface and geometric analysis of them indicates that the maximum crack velocity is similar to 800 m s(-1), which corresponds to similar to 0.32 times the shear wave speed. Fractography reveals that the sharp crack nucleation at the notch tip occurs at the mid-section of the specimens with the observation of flat and half-penny-shaped cracks. On this basis, we conclude that the crack initiation in brittle BMGs is stress-controlled and occurs through hydrostatic stress-assisted cavity nucleation ahead of the notch tip. High magnification scanning electron and atomic force microscopies of the dynamic crack growth regions reveal highly organized, nanoscale periodic patterns with a spacing of similar to 79 nm. Juxtaposition of the crack velocity with this spacing suggests that the crack takes similar to 10(-10) s for peak-to-peak propagation. This, and the estimated adiabatic temperature rise ahead of the propagating crack tip that suggests local softening, is utilized to critically discuss possible causes for the nanocorrugation formation. Taylor's fluid meniscus instability is unequivocally ruled out. Then, two other possible mechanisms, viz. (a) crack tip blunting and resharpening through nanovoid nucleation and growth ahead of the crack tip and eventual coalescence, and (b) dynamic oscillation of the crack in a thin slab of softened zone ahead of the crack-tip, are critically discussed. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Isolating single primary rat hippocampal neurons and astrocytes on ultra-thin patterned parylene-C/silicon dioxide substrates

We report here the patterning of primary rat neurons and astrocytes from the postnatal hippocampus on ultra-thin parylene-C deposited on a silicon dioxide substrate, following observations of neuronal, astrocytic and nuclear coverage on strips of different lengths, widths and thicknesses. Neuronal and glial growth was characterized 'on', 'adjacent to' and 'away from' the parylene strips. In addition, the article reports how the same material combination can be used to isolate single cells along thin tracks of parylene-C. This is demonstrated with a series of high magnification images of the experimental observations for varying parylene strip widths and thicknesses. Thus, the findings demonstrate the possibility to culture cells on ultra-thin layers of parylene-C and localize single cells on thin strips. Such work is of interest and significance to the Neuroengineering and Multi-Electrode Array (MEA) communities, as it provides an alternative insulating material in the fabrication of embedded micro-electrodes, which can be used to facilitate single cell stimulation and recording in capacitive coupling mode. © 2010 Elsevier Ltd.

Control of wettability of carbon nanotube array by reversible dry oxidation for superhydrophobic coating and supercapacitor applications

In this thesis, dry chemical modification methods involving UV/ozone, oxygen plasma, and vacuum annealing treatments are explored to precisely control the wettability of CNT arrays. By varying the exposure time of these treatments the surface concentration of oxygenated groups adsorbed on the CNT arrays can be controlled. CNT arrays with very low amount of oxygenated groups exhibit a superhydrophobic behavior. In addition to their extremely high static contact angle, they cannot be dispersed in DI water and their impedance in aqueous electrolytes is extremely high. These arrays have an extreme water repellency capability such that a water droplet will bounce off of their surface upon impact and a thin film of air is formed on their surface as they are immersed in a deep pool of water. In contrast, CNT arrays with very high surface concentration of oxygenated functional groups exhibit an extreme hydrophilic behavior. In addition to their extremely low static contact angle, they can be dispersed easily in DI water and their impedance in aqueous electrolytes is tremendously low. Since the bulk structure of the CNT arrays are preserved during the UV/ozone, oxygen plasma, and vacuum annealing treatments, all CNT arrays can be repeatedly switched between superhydrophilic and superhydrophobic, as long as their O/C ratio is kept below 18%.

The effect of oxidation using UV/ozone and oxygen plasma treatments is highly reversible as long as the O/C ratio of the CNT arrays is kept below 18%. At O/C ratios higher than 18%, the effect of oxidation is no longer reversible. This irreversible oxidation is caused by irreversible changes to the CNT atomic structure during the oxidation process. During the oxidation process, CNT arrays undergo three different processes. For CNT arrays with O/C ratios lower than 40%, the oxidation process results in the functionalization of CNT outer walls by oxygenated groups. Although this functionalization process introduces defects, vacancies and micropores opening, the graphitic structure of the CNT is still largely intact. For CNT arrays with O/C ratios between 40% and 45%, the oxidation process results in the etching of CNT outer walls. This etching process introduces large scale defects and holes that can be obviously seen under TEM at high magnification. Most of these holes are found to be several layers deep and, in some cases, a large portion of the CNT side walls are cut open. For CNT arrays with O/C ratios higher than 45%, the oxidation process results in the exfoliation of the CNT walls and amorphization of the remaining CNT structure. This amorphization process can be implied from the disappearance of C-C sp2 peak in the XPS spectra associated with the pi-bond network.

The impact behavior of water droplet impinging on superhydrophobic CNT arrays in a low viscosity regime is investigated for the first time. Here, the experimental data are presented in the form of several important impact behavior characteristics including critical Weber number, volume ratio, restitution coefficient, and maximum spreading diameter. As observed experimentally, three different impact regimes are identified while another impact regime is proposed. These regimes are partitioned by three critical Weber numbers, two of which are experimentally observed. The volume ratio between the primary and the secondary droplets is found to decrease with the increase of Weber number in all impact regimes other than the first one. In the first impact regime, this is found to be independent of Weber number since the droplet remains intact during and subsequent to the impingement. Experimental data show that the coefficient of restitution decreases with the increase of Weber number in all impact regimes. The rate of decrease of the coefficient of restitution in the high Weber number regime is found to be higher than that in the low and moderate Weber number. Experimental data also show that the maximum spreading factor increases with the increase of Weber number in all impact regimes. The rate of increase of the maximum spreading factor in the high Weber number regime is found to be higher than that in the low and moderate Weber number. Phenomenological approximations and interpretations of the experimental data, as well as brief comparisons to the previously proposed scaling laws, are shown here.

Dry oxidation methods are used for the first time to characterize the influence of oxidation on the capacitive behavior of CNT array EDLCs. The capacitive behavior of CNT array EDLCs can be tailored by varying their oxygen content, represented by their O/C ratio. The specific capacitance of these CNT arrays increases with the increase of their oxygen content in both KOH and Et4NBF4/PC electrolytes. As a result, their gravimetric energy density increases with the increase of their oxygen content. However, their gravimetric power density decreases with the increase of their oxygen content. The optimally oxidized CNT arrays are able to withstand more than 35,000 charge/discharge cycles in Et4NBF4/PC at a current density of 5 A/g while only losing 10% of their original capacitance.

Characterizing the mechanics of cultured cell monolayers.

One-cell-thick monolayers are the simplest tissues in multicellular organisms, yet they fulfill critical roles in development and normal physiology. In early development, embryonic morphogenesis results largely from monolayer rearrangement and deformation due to internally generated forces. Later, monolayers act as physical barriers separating the internal environment from the exterior and must withstand externally applied forces. Though resisting and generating mechanical forces is an essential part of monolayer function, simple experimental methods to characterize monolayer mechanical properties are lacking. Here, we describe a system for tensile testing of freely suspended cultured monolayers that enables the examination of their mechanical behavior at multi-, uni-, and subcellular scales. Using this system, we provide measurements of monolayer elasticity and show that this is two orders of magnitude larger than the elasticity of their isolated cellular components. Monolayers could withstand more than a doubling in length before failing through rupture of intercellular junctions. Measurement of stress at fracture enabled a first estimation of the average force needed to separate cells within truly mature monolayers, approximately ninefold larger than measured in pairs of isolated cells. As in single cells, monolayer mechanical properties were strongly dependent on the integrity of the actin cytoskeleton, myosin, and intercellular adhesions interfacing adjacent cells. High magnification imaging revealed that keratin filaments became progressively stretched during extension, suggesting they participate in monolayer mechanics. This multiscale study of monolayer response to deformation enabled by our device provides the first quantitative investigation of the link between monolayer biology and mechanics.

Synthesis and photoluminescence of the Y2O3 : Eu3+ phosphor nanowires in AAO template

The monodisperse array and nanowires Of Y2O3:Eu3+ phosphor were synthesized using anodic aluminum oxide (AAO) template by sol-gel method. Scanning electron microscope (SEM) images indicated that Y2O3:Eu3+ nanowires are parallelly arranged, all of which are in uniform diameter of about 50 nm. The high-magnification SEM image showed that each nanowire is composed of a lot of agglutinating particles. The patterns of selected-area electron diffraction confirmed that Y2O3:EU3+ nanowires mainly consist of polycrystalline materials. Excitation and emission spectra Of Y2O3:E U3+/AAO composite films were measured. The characteristic red emission peak of EU3+ ion attributed to D-5(0)-->F-7(2) transition in Y2O3:EU3+/AAO nanowires broadened its halfwidth.

Nonisothermal crystallization behavior of poly (L-lactide)-poly(ethylene glycol) dibloick copolymer

The nonisothermal crystallization behavior of poly (L-lactide)-poly(ethylene glycol) ( PLLA-PEG) diblock copolymer was studied by means of real-time WAXD, DSC and POM, and Ozawa equation was used to analyze the kinetics of PLLA-PEG under nonisothermal crystallization conditions. During the crystallization of the high-T-m block (PLLA), the low-T-m block (PEG) acts as a noncrystalline diluent, and the crystallization behavior of PLLA obeys the Ozawa theory. When the PEG block begins to crystallize, the PLLA phase is always partially solidified and the presence of the spherulitic microstructure of PLLA profoundly restricts its crystallization behavior, which results in that the overall crystallization process does not obey the Ozawa equation. Furthermore, the study of the crystalline morphology of PLLA-PEG at different cooling rates indicates that when the cooling rate is from low to high, the crystalline morphology undergoes a transformation from the ring-banded spherulites to the typical Maltese cross spherulites, which experiences the mixed crystalline morphologies of ring-banded and typical Maltese cross spherulites, and the spherulitic size becomes smaller.

Cannabinoid Receptor influences Chromatin Remodelling in Mouse Spermatids by affecting Content of Transition Protein 2 mRNA and Histone Replacement

Marijuana smokers and animals treated with ?9-tetrahydrocannabinol, THC, the principal component of marijuana, show alterations of sperm morphology suggesting a role for cannabinoids in sperm differentiation and/or maturation. Since the cannabinoid receptor 1 (CNR1) activation appears to play a pivotal role in spermiogenesis, the developmental stage where DNA is remodeled, we hypothesized that CNR1 receptors might also influence chromatin quality in sperm. We used Cnr1 null mutant (Cnr1-/-) mice to study the possible role of endocannabinoids on sperm chromatin during spermiogenesis. We demonstrated that CNR1 activation regulated chromatin remodeling of spermatids by either increasing Tnp2 levels or enhancing histone displacement. Comparative analysis of WT, Cnr1+/- and Cnr1-/- animals suggested the possible occurrence of haploinsufficiency for Tnp2 turnover control by CNR1, while histone displacement was disrupted to a lesser extent. Further, flow cytometry analysis demonstrated that the genetic loss of Cnr1 decreased sperm chromatin quality and was associated with sperm DNA fragmentation. This damage increased during epididymal transit, from caput to cauda. Collectively, our results show that the expression/activity of CNR1 controls the physiological alterations of DNA structure during spermiogenic maturation and epididymal transit. Given the deleterious effects of sperm DNA damage on male fertility, we suggest that the reproductive function of marijuana users may also be impaired by deregulation of the endogenous endocannabinoid system.

Near-field spatial imaging of a Ni-like Ag 140-angstrom x-ray laser

We measure the two-dimensional, near-field spatial distribution of a 140-Angstrom nickel-like silver x-ray laser at the output aperture with high magnification using a curved multilayer x-ray mirror to image the output onto an x-ray charge-coupled device camera. Lasing is created by illuminating silver slab targets with a pair of 75 ps laser pulses separated by 2.2 nsec from the Vulcan laser. The two-dimensional, high-resolution, spatial image shows the x-ray laser source size and its position relative to the target surface. A dramatic change in both the position and source size are observed for the refraction compensating curved target as compared with the flat targets.

Brittle-ductile transition during diamond turning of single crystal silicon carbide

In this experimental study, diamond turning of single crystal 6H-SiC was performed at a cutting speed of 1 m/s on an ultra-precision diamond turning machine (Moore Nanotech 350 UPL) to elucidate the microscopic origin of ductile-regime machining. Distilled water (pH value 7) was used as a preferred coolant during the course of machining in order to improve the tribological performance. A high magnification scanning electron microscope (SEM FIB- FEI Quanta 3D FEG) was used to examine the cutting tool before and after the machining. A surface finish of Ra=9.2 nm, better than any previously reported value on SiC was obtained. Also, tremendously high cutting resistance was offered by SiC resulting in the observation of significant wear marks on the cutting tool just after 1 km of cutting length. It was found out through a DXR Raman microscope that similar to other classical brittle materials (silicon, germanium, etc.) an occurrence of brittle-ductile transition is responsible for the ductile-regime machining of 6H-SiC. It has also been demonstrated that the structural phase transformations associated with the diamond turning of brittle materials which are normally considered as a prerequisite to ductile-regime machining, may not be observed during ductile-regime machining of polycrystalline materials.

Laser-driven x-ray and neutron source development for industrial applications of plasma accelerators

Pulsed beams of energetic x-rays and neutrons from intense laser interactions with solid foils are promising for applications where bright, small emission area sources, capable of multi-modal delivery are ideal. Possible end users of laser-driven multi-modal sources are those requiring advanced non-destructive inspection techniques in industry sectors of high value commerce such as aerospace, nuclear and advanced manufacturing. We report on experimental work that demonstrates multi-modal operation of high power laser-solid interactions for neutron and x-ray beam generation. Measurements and Monte Carlo radiation transport simulations show that neutron yield is increased by a factor ∼2 when a 1 mm copper foil is placed behind a 2 mm lithium foil, compared to using a 2 cm block of lithium only. We explore x-ray generation with a 10 picosecond drive pulse in order to tailor the spectral content for radiography with medium density alloy metals. The impact of using >1 ps pulse duration on laser-accelerated electron beam generation and transport is discussed alongside the optimisation of subsequent bremsstrahlung emission in thin, high atomic number target foils. X-ray spectra are deconvolved from spectrometer measurements and simulation data generated using the GEANT4 Monte Carlo code. We also demonstrate the unique capability of laser-driven x-rays in being able to deliver single pulse high spatial resolution projection imaging of thick metallic objects. Active detector radiographic imaging of industrially relevant sample objects with a 10 ps drive pulse is presented for the first time, demonstrating that features of 200 μm size are resolved when projected at high magnification.

Avaliação do efeito de metais pesados na fertilidade do ratinho

A infertilidade é um problema actual que afecta cerca de 8 a 12% dos casais em idade fértil, sendo 50% dos casos atribuídos ao factor masculino. A exposição ocupacional e/ou ambiental a metais pesados representa uma das suas principais causas. O chumbo, o cádmio e o crómio são metais com elevada utilização industrial e muito persistentes no ambiente, sendo motivo de grande preocupação devido aos seus efeitos na saúde reprodutiva dos trabalhadores e da população em geral. Neste trabalho estudaram-se os efeitos do cloreto de chumbo (PbCl2), cloreto de cádmio (CdCl2) e cromato de potássio (K2CrO4) na fertilidade, usando como modelo ratinhos machos ICR-CD1. Os ratinhos foram injectados subcutaneamente com 74 e 100 mg de PbCl2/kg pc ou com 5 e 10 mg de K2CrO4/kg pc, respectivamente, durante 4 dias consecutivos ou com 1, 2 e 3 mg de CdCl2/kg pc numa única injecção. Nos ensaios com PbCl2 e K2CrO4 os animais foram sacrificados 5 e 35 dias após o início da exposição, enquanto que nos ensaios com CdCl2 os animais foram sacrificados após 24 horas e 35 dias. O cloreto de chumbo não alterou a histologia do testículo nem do epidídimo, mas induziu um aumento da percentagem de células em fase S no testículo. O cloreto de chumbo alterou também alguns parâmetros dos espermatozóides, tais como a motilidade, morfologia e integridade do acrossoma. Contudo, não foram observados efeitos na integridade do DNA ou na estrutura da cromatina. O cloreto de cádmio induziu lesões severas e não reversíveis nos testículos que, após 35 dias, reverteram em necrose testicular. O cloreto de cádmio alterou ainda as subpopulações de células testiculares após 24 horas e induziu IMS no testículo após 35 dias. Em consequência das lesões no testículo, a densidade espermática foi severamente afectada após 35 dias. A exposição ao cloreto de cádmio afectou também a morfologia, a motilidade e a integridade acrossómica nos espermatozóides. O cloreto de cádmio induziu ainda fragmentação do DNA nestas células após 35 dias. O cromato de potássio alterou a morfologia dos espermatozóides e a integridade do acrossoma, sobretudo nos animais sacrificados após 35 dias. Verificou-se ainda uma redução da motilidade dos espermatozóides. Não foram detectados efeitos genotóxicos nos espermatozóides, devido à acção do K2CrO4 nas doses testadas. Dos parâmetros avaliados neste trabalho, destacam-se duas novas abordagens, nomeadamente o programa informático Snakes e a análise do conteúdo em DNA de células de testículo, a partir de material incluído em parafina. O Snakes permitiu fazer medições rigorosas do diâmetro dos tubos seminíferos, enquanto que a fixação de amostras de testículo de ratinhos em formol tamponado e inclusão em parafina resultou numa boa preservação do DNA, possibilitando assim a quantificação das subpopulações de células testiculares por citometria de fluxo. Os resultados obtidos para os diferentes parâmetros testados indicam que a motilidade dos espermatozóides e a integridade do acrossoma sejam parâmetros sensíveis à toxicidade de metais. O acrossoma aparenta ser um dos principais alvos da toxicidade dos metais e cuja reacção acrossómica prematura pode reduzir a capacidade do espermatozóide para fertilizar o oócito. Assim, este trabalho representa uma contribuição para uma melhor compreensão dos efeitos do chumbo, cádmio e crómio na fertilidade masculina.

Isolating single primary rat hippocampal neurons & astrocytes on ultra-thin patterned parylene-C/silicon dioxide substrates

We report here the patterning of primary rat neurons and astrocytes from the postnatal hippocampus on ultra-thin parylene-C deposited on a silicon dioxide substrate, following observations of neuronal, astrocytic and nuclear coverage on strips of different lengths, widths and thicknesses. Neuronal and glial growth was characterized ‘on’, ‘adjacent to’ and ‘away from’ the parylene strips. In addition, the article reports how the same material combination can be used to isolate single cells along thin tracks of parylene-C. This is demonstrated with a series of high magnification images of the experimental observations for varying parylene strip widths and thicknesses. Thus, the findings demonstrate the possibility to culture cells on ultra-thin layers of parylene-C and localize single cells on thin strips. Such work is of interest and significance to the Neuroengineering and Multi-Electrode Array (MEA) communities, as it provides an alternative insulating material in the fabrication of embedded micro-electrodes, which can be used to facilitate single cell stimulation and recording in capacitive coupling mode.

Testicular traits as selection criteria for young Nellore bulls

The objective of this study was to evaluate the possible use of biometric testicular traits as selection criteria for young Nellore bulls using Bayesian inference to estimate heritability coefficients and genetic correlations. Multitrait analysis was performed including 17,211 records of scrotal circumference obtained during andrological assessment (SCAND) and 15,313 records of testicular volume and shape. In addition, 50,809 records of scrotal circumference at 18 mo (SC18), used as an anchor trait, were analyzed. The (co) variance components and breeding values were estimated by Gibbs sampling using the Gibbs2F90 program under an animal model that included contemporary groups as fixed effects, age of the animal as a linear covariate, and direct additive genetic effects as random effects. Heritabilities of 0.42, 0.43, 0.31, 0.20, 0.04, 0.16, 0.15, and 0.10 were obtained for SC18, SCAND, testicular volume, testicular shape, minor defects, major defects, total defects, and satisfactory andrological evaluation, respectively. The genetic correlations between SC18 and the other traits were 0.84 (SCAND), 0.75 (testicular shape), 0.44 (testicular volume), -0.23 (minor defects), -0.16 (major defects), -0.24 (total defects), and 0.56 (satisfactory andrological evaluation). Genetic correlations of 0.94 and 0.52 were obtained between SCAND and testicular volume and shape, respectively, and of 0.52 between testicular volume and testicular shape. In addition to favorable genetic parameter estimates, SC18 was found to be the most advantageous testicular trait due to its easy measurement before andrological assessment of the animals, even though the utilization of biometric testicular traits as selection criteria was also found to be possible. In conclusion, SC18 and biometric testicular traits can be adopted as a selection criterion to improve the fertility of young Nellore bulls.

Efeito da idade sobre as principais características andrológicas de touros Brangus- Efeito da idade sobre as principais características andrológicas de touros BrangusIbagé criados extensivamente no estado do Mato Grosso do Sul - Brasil Ibagé criados extensivamente no estado do Mato Grosso do Sul - Brasil

Background: Bull fertility is extremely important for beef cattle production systems and has a multiplier impact on the economical and zootechnical indexes of the herd. Bulls raised in tropical conditions may present varied seminal characteristics due to, among other causes, different management practices and quality of pastures. Another factor that influences the semen characteristics is the age of the sire. The reproductive potential of bull evaluated through the andrological exam aims to ensure the semen quality and to improve the herd reproductive efficiency. The aim of this study was to evaluate the main semen parameters of Brangus-Ibage bulls extensively reared in eastern Mato Grosso do Sul state and to verify the effect of age on the andrological characteristics analyzed. It was also evaluated the correlation between age, scrotal circumference, and physical and morphological sperm characteristics produced by the Brangus bulls.Materials, Methods & Results: The study took place in the month of July 2010, during the routine andrological examination of 168 synthetic Brangus-Ibage bulls (5/8 Angus x 3/8 Nelore), belonging to the same property. For data analysis the animals were divided by age groups: animals younger than 4 years (Age I), animals between 4 and 8 years of age (Age II), and animals between 8 and 15 years of age (Age III). In another analysis, the animals were grouped according to the sperm motility pattern obtained from the semen collection: sperm motility lower than 40% (Motility I), sperm motility between 40 and 70% (Motility II) and sperm motility between 70 and 90% (Motility III). The results of the present study demonstrated an effect of age (P < 0.05) on the following androgical characteristics: scrotal circumference, ejaculate volume, sperm vigor, major defects, minor defects and total defects. It was also observed that the animals with higher sperm motility presented higher (P < 0.05) scrotal circumference, and lower (P < 0.05) percentages of major and total defects. Among the andrological characteristics evaluated in the present work, it was observed positive correlations between age and scrotal circumference (R =0.299; P =0.000), age and volume of ejaculate (R =0.161; P =0.037), age and major defects (R =0.188; P =0.015), sperm motility and scrotal circumference (R =0.245; P =0.001), sperm motility and sperm vigor (R =0.483; P =0.000), and between major defects and total defects (R =0.946; P =0.000). Also, negative correlations were observed between sperm motility and total defects (R =-0.372; P =0.000), sperm vigor and major defects (R =-0.498; P =0.000), and sperm vigor and total defects (R =-0.432; P =0.000).Discussion: Based on the results of this study it was concluded that the Brangus-Ibage bulls utilized for natural breeding in eastern Mato Grosso do Sul, Brazil, presented satisfactory semen quality taking into account the quality of the pastures where the animals were located. In addition, the scrotal circumference, the ejaculate volume, the sperm vigor, and the percentage of morphological characteristics were influenced by the age of the bulls. Therefore, considering the production system and the environmental conditions, the animals with age between 4 and 8 years were superior regarding the sperm parameters evaluated.